Projection laser scanner producing a narrow scan volume

ABSTRACT

A bar code scanner for stationary disposition at a counter to projecting a scanning pattern comprising first, second, third, fourth and fifth groups of parallel scan lines within a relatively narrow, yet diverging, volume, e.g., pyramid, cone, etc., centered about a projection axis. The scanner includes a compact housing mounted on an adjustible base. The housing includes a window, five stationary mirrors, a laser diode, a rotating reflective polygon for sweeping the laser beam from the diode across the mirrors and out a window so that the projection axis is substantially but not precisely perpendicular to the window. The scanner also includes a fixed curved collecting mirror and a concentrating lens to focus light which is reflected off of a bar code to a photodetector. One mirror extends along an axis parallel to the transverse axis to produce the first group of scan lines. The second and third mirrors are disposed opposite each other close to and laterally of the polygon and extending along respective axes at a small acute angle, e.g., 8 degrees, to the longitudinal axis to produce respective ones of the second and third group of scan lines. The fourth and fifth mirrors are disposed between the second and third reflecting mirrors, respectively, and each extends along a respective axis at a substantial acute angle, e.g., 48 degrees, to the longitudinal axis to produce respective ones of the fourth and fifth group of scan lines.

BACKGROUND OF THE INVENTION

This invention relates generally to laser scanning apparatus and moreparticularly to fix-mounted, e.g., counter type, laser scanningapparatus.

Various laser-based scanning systems have been disclosed in the patentliterature and many are commercially available to read bar codes, e.g.,the uniform product code, which is imprinted on packaging for product,or on the product itself, or on some other item.

One type of scanning system is referred to as a counter or "slotscanner". Such devices are generally mounted within a housing in acheckout counter of a supermarket or other retail establishment, andinclude a window at the top thereof through which a scanning pattern isprojected. The scanning pattern is created by a laser and associatedoptical components, e.g., mirrors, etc., which typically produce pluralscan lines which are either parallel to one another and/or intersect oneanother. When an item bearing a bar code is brought into the field ofthe scan pattern so that the pattern traverses the bar code light isreflected off of the bar code and is received back through the window ofthe slot scanner, whereupon decoding means converts the received lightinto an electrical signal indicative of the bar code. These signals canthen be utilized to identify the article bearing the code and providepricing information.

In order to ensure that a bar code is traversed suffiiently so that itcan be read accurately irrespective of its orientation within the scanpattern, prior art counter scanners have utilized various opticalconfigurations including mirrors, prisms, and the like to fold the laserbeam and create complex patterns. Examples of such patterns are combpatterns, orthogonal patterns, interlaced patterns, star-like patterns,etc. While such patterns may be suitable for their purposes, the meansfor creating them has resulted in housings which were quite large insize.

In my U.S. Pat. No. 4,713,532 there is disclosed a counter or slotscanner producing an aggressive scanning pattern having three rasteredgroups of intersecting scan lines to form a large "sweet spot" to enablethe bar code to be read omnidirectionally, i.e., irrespective of itsorientation with respect to the scanner. That scanner is housed within avery compact, small footprint housing which is arranged to be mountedunder a counter or disposed on a counter. Depending upon the orientationof the scanner, its window may be horizontal or at some otherorientation, e.g., vertical. Devices embodying the teachings of thatpatent have been sold by the assignee of that patent (and of thisapplication), Metrologic Instruments, Inc., under the designation MS260.

Metrologic Instruments, Inc. has also sold other compact counter or slotscanners under the designation MS360. Those scanners also produce abroad, aggressive scan pattern. In that case the pattern is made up offive rastered groups of intersecting scan lines.

While the aforementioned counter scanners have proved suitable for theirintended purposes it has been determined that in certain applicationsthe production of a broad scanning pattern is less than optimum Forexample, in some check-out counter applications it is desirable tocreate a scanning pattern which, although aggressive, is confined withina relatively narrow volume, to prevent unintentional scanning of nearbyobjects. Hand-held scanners while providing for scanning within aconfined volume (to prevent unintentional scanning), nevertheless sufferfrom various drawbacks, one of which being aggressiveness of thescanning pattern.

Thus, the need exists for a scanner device which combines theversatility of a hand-held scanner with the aggressiveness of a counteror slot scanner.

In many mass merchandizing applications it is desirable to have ascanner with the aggressiveness of a counter or slot scanner but whichdoes require that the scanner be mounted or disposed with its window onthe counter where it may present a snagging hazard to bar coded items,e.g., garments on hangers or hooks, if they are dragged across thecounter for scanning. In other applications, e.g., where bar coded itemsare packaged in such a way as to require that they not be inverted, itis also desirable to provide an aggressive, fixed mount scanner toproject the scanning pattern down toward the counter from above so thatitems can be scanned right-side-up.

Thus, the need also exists for a counter mounted scanner which canproject an aggressive scanning pattern from the side or above to scanitems brought into the pattern, yet which pattern is relatively confinedto minimize counter space required to be clear of bar coded items.

Some commercially available scanners are arranged to be disposed ormounted to project a scanning pattern somewhat laterally to act as a"projection scanner". Examples of such scanners are the following: the"FREEDOM" scanner sold by Spectra Physics, the "7852" scanner sold byNCR, the "OMNISCAN" scanner sold by Microvideo, and the "SLIMSCAN"scanner sold by Fujitsu. While such scanners are generally suitable fortheir intended purposes they all suffer from one or more drawbacks, suchas somewhat large housing and/or "footprint" size, amount of counterspace to be kept clear of bar coded items, somewhat restricted workingrange, inability to scan all types of bar codes omnidirectionally andlack of agressiveness of scan pattern.

OBJECTS OF THE INVENTION

Accordingly, it is a general object of this invention to overcome thedisadvantages of the prior art.

It is a further object of this invention to provide an extremelycompact, fixed mounted scanning unit which overcomes the disadvantagesof the prior art.

It is still a further object of this invention to provide a fixedmounted scanning unit which is arranged to project a rich scanningpattern into a confined volume for scanning a bar coded item broughttherein irrespective of the orientation of the bar code.

It is yet a further object of this invention to provide an extremelycompact fixed mounted scanning unit which is arranged to project a richscanning pattern laterally or downward into a confined volume forscanning a bar coded item brought therein.

SUMMARY OF THE INVENTION

These and other objects of the instant invention are achieved byproviding a laser scanning device arranged to be stationarily supportedat a counter for projecting a scanning pattern adjacent the counter,e.g., in a generally laterally outward direction with respect to saidcounter, and into which pattern a code having portions of differentreflectivity, e.g., a bar code, to be scanned is located The scanningpattern comprises plural, e.g., five, groups of plural, e.g., four,parallel scan lines.

The device basically comprises a compact housing, laser beam generatingmeans, laser beam sweeping means, light reflecting means, lightcollecting means, and a window having a longitudinal axis and atransverse axis. The longitudinal and transverse axes of the windowdefine a plane through which the scanning pattern is projected. Thescanning pattern is generally confined within a relatively narrow, yetdiverging, volume, e.g., pyramid, cone, frustum, etc., centered about aprojection axis which is substantially but not precisely perpendicularto the plane of the window. For example, the projection axis may be atany angle within the range of from a slight deviation from preciseperpendicularity up to approximately thirty (30) degrees therefrom. Thelight reflecting means comprises plural, e.g., at least five (5),reflecting members, e.g., mirrors. The laser beam sweeping means, e.g.,a polygonal member having four (4) reflective surfaces arranged to berotated about a rotation axis, serves to sweep the laser beam across thereflecting members, whereupon each of the reflecting members produces arespective one of the groups of lines of the pattern.

In one preferred embodiment of the device there are five reflectingmembers. The first reflecting member is disposed on a first axis of thehousing opposite the polygonal member and extends along an axis parallelto the transverse axis. The first reflecting mirror is arranged toreflect the laser beam swept thereacross directly out through the windowto produce the first group of scan lines. The second and thirdreflecting members are disposed on opposite sides of the first axis andclosely adjacent laterally of the polygonal member. The first axis isparallel to the longitudinal axis and perpendicular to the transverseaxis. Each of the second and third members extends along a respectiveaxis at a small acute angle, e.g., 8 degrees, to the first axis and isarranged to reflect the laser beam swept thereacross directly outthrough the window to produce respective ones of the second and thirdgroups of scan lines. The fourth and fifth reflecting members aredisposed on opposite sides of the central axis between the second andthird reflecting members, respectively, and each extends along arespective axis at a substantial acute angle, e.g., 48 degrees, to thelongitudinal axis. Each of the fourth and fifth reflecting members isarranged to reflect the laser beam swept thereacross directly outthrough the window to produce respective ones of the fourth and fifthgroups of scan lines.

The light receiving means comprises light focussing means and transducermeans. The transducer means is arranged to receive light reflected fromthe code which enters the window, is reflected by the reflecting membersand the beam sweeping means, e.g., the reflecting surfaces of thepolygon, and is focussed by the focussing means, to convert it into anelectrical signal indicative of the code.

The light focussing means basically comprises a collecting mirror havinga concave reflective surface arranged to receive light from the beamsweeping means, e.g., reflective surfaces of the polygon, and to directit to a concentrating lens. The lens acts to further focus the lightonto the transducer means.

DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of one embodiment of a laser scanningdevice constructed in accordance with the subject invention showndisposed on a conventional check-out counter of a retail establishment;

FIG. 2 is an enlarged top plan view, partially in section, of thescanning device shown in FIG. 1;

FIG. 3 is a sectional view taken along lines 3--3 of FIG. 2;

FIG. 4 is a sectional view taken along lines 4--4 of FIG. 3;

FIG. 5 is a plan view of the scanning pattern produced by the deviceshown in FIG. 1 at the plane of its window;

FIG. 6 is a top plan view, partially in section, similar to that of FIG.2, but showing an alternative embodiment of the scanning device shown inFIG. 1;

FIG. 7 is a sectional view taken along lines 7--7 of FIG. 6; and

FIG. 8 is a plan view of the scanning pattern produced by the deviceshown in FIG. 6 at the plane of the scanner's window.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to various figures of the drawing wherein like referencecharacters refer to like parts there is shown in FIG. 1, one embodiment20 of a retroreflective, laser bar-code, scanner constructed inaccordance with this invention.

The scanner 20 is mounted on a base 22 disposed on a counter 24, such asa checkout counter of a store, to project a scanning pattern 26 adjacentthe counter. In the embodiment shown in FIGS. 1 and 5 the scanningpattern is projected laterally or downward over the counter. Thisorientation merely constitutes one of many orientations of the scanningpattern. In any event an article, such as a food container (not shown),having a conventional bar code (not shown), such as the UPC code,printed thereon is brought into the scanning pattern 26 by the checkoutclerk, to enable the lines making up the pattern to sweep across thecode to illuminate it with laser light, whereupon light reflected offthe bar code is received back through the window by the components ofthe scanner. Such components process the received light into a bar codebearing electrical signal, as is conventional.

The scanning pattern of the subject invention is confined within arelatively narrow, yet diverging volume centered about a projection axisfrom the scanner (as will be described later) and includes plural groupsof intersecting scan lines to create a "rich" pattern. This "rich"pattern ensures that sufficient lines of the pattern will sweep acrossthe entire bar code to enable the proper reading or decoding thereof byconventional decoding means located within the scanner 20, irrespectiveof the orientation of the bar code within the scanning pattern.Moreover, by virtue of the fact that the volume or space in whichscanning pattern is projected is somewhat narrow or confined, the amountof counter space which must be kept clear of other bar coded items toenable the proper scanning of the selected bar coded item, can be keptto a minimum. This should be contrasted with the use of conventional"slot-type" scanners, if mounted on a counter to project the scanningpattern thereabove. In such an arrangement the slot scanner producessuch a wide or divergent pattern that a large amount of counter spacemust be reserved for scanning, and thus cannot be used for any otherpurpose, e.g., cannot be used to display for advertizing or promotionalpurposes any item bearing a bar code, since the scanner may read thatbar code if it is within the scan pattern.

As is conventional the decoder utilized in the scanner 20 is arranged toprovide electrical signals indicative of the decoded symbol toperipheral equipment, such as a conventional electronic cash register27.

As will be described hereinafter, the scanner 20 is disposed within ahousing 28 which is extremely compact. For example, in one commercialembodiment of the invention, the housing has a height of approximately6.5 inches (165 mm), a width of approximately 6.5 inches (165 mm), and athickness of approximately 3 inches (76 mm). The scanner housing 28includes a window 30 through which the confined scanning pattern 26 isprojected.

As can be seen in FIG. 1 the base 22 on which the scanner is mounted isalso extremely compact in size. Moreover, the base 22 is arranged to beadjusted to various orientations to hold the scanner housing with thewindow 30 in any desired orientation so that the scanning pattern isprojected in any desired orientation with respect to the counter, e.g.,laterally outward and slightly downward toward the counter as shown inFIGS. 1 and 5, upward with respect to the counter like that of aconventional slot scanner (not shown), or in any other desiredorientation (not shown).

Before describing the details of the construction of the scanner 20, thescanning pattern produced thereby will be described. That pattern isshown clearly in FIGS. 1 and 5 and is produced within the scannerhousing 28 and projected thereout through the window 30. The window 30is a generally planar, optically transparent member defined by alongitudinal axis 32 and a normally intersecting transverse axis 34. Thescanning pattern 26 is projected into a confined space or volume 38 (seeFIG. 1), which as mentioned earlier is a relatively narrow, yetdiverging and is centered about a projection axis 38. The divergingvolume 36 containing the pattern may be of any shape, e.g. pyramidal,conical, irregular, etc., depending upon the length of the various linesof the pattern (i.e., the "envelope" defined by the end points of eachline of the pattern) and may be established by the size of the scanner'smirrors and/or the size and shape of the window. In the interest ofdrawing simplicity the envelope defining volume 36 is shown as beingpyramidal and as such is merely exemplary of the myriad of shapespossible. The projection axis 38 extends substantially perpendicular tothe plane of the window. By "substantially perpendicular" it is meantthat the projection axis is not precisely pependicular to the plane ofthe window, i.e., it deviates from perpendicularity up to a small acuteangle, e.g., thirty (30) degrees, to perpendicularity. The reason thatthe projection axis is not precisely perpendicular to the plane of thewindow is to preclude overloading of the transducer, e.g. thephotodetector (to be described later), in the light receiving meanswhich could occur if the exiting laser beam was reflected back off thewindow to the transducer.

It should be pointed out at this juncture that the lines making up thescanning pattern are preestablished in configuration and orientationwith respect to one another, but appear differently, depending upon theshape and position of the surface upon which the pattern is projectedand depending upon the distance of the surface from the scanner window.In FIG. 1 the scanning pattern 26 shown is merely schematic andindicative of a typical pattern projected on a flat surface within thevolume 36, approximately six inches from the window 30 and generallyperpendicular to the projection axis. In FIG. 5 the scanning pattern isshown as it appears within housing at the plane of the window 30.

As can be seen the scanning pattern 26 basically consists of five groups26A, 26B, 26C, 26D, and 26E of plural, scan lines 40. The scan lines ineach group are disposed generally parallel to one another and in theembodiment of FIGS. 1-4 are preferably substantially equidistantlyspaced in a "raster-like" configuration. In the embodiment shown hereinthere are four scan lines 40 in each group 38A-38E.

The lines 40 making up group 26A are disposed generally parallel to thetransverse axis 34 of the window. These lines, when projected in volume36, are somewhat horizontal and are very powerful in their ability toreadily scan "picket fence" oriented bar codes, whether truncated ornot. The lines 40 making up group 26B intersect the lines 40 of group26A and extend at a substantial acute angle, e.g., 28°, to longitudinalaxis 32 to be oriented generally diagonally when projected into volume36. The lines 40 making up group 26C are mirror images of the linesmaking up group 26B and are disposed on the opposite side of thelongitudinal axis 32 from the lines making up that group. The two groups26B and 26C serve to readily scan bar codes which are tilted withrespect to a "roll" axis (not shown) generally perpendicular to thewindow. The lines 40 of groups 26D are each oriented at a small acuteangle, e.g., 8°, to the longitudinal axis 32 so as to be orientedgenerally vertically when projected into the volume 36. The lines 40making up group 26E are mirror images of the lines making up group 26Dand are disposed on the opposite sides of the longitudinal axis from thelines making up that group. The groups 26D and 26E serve to readily scan"ladder" oriented bar codes.

The rastered lines 40 of the groups substantially fill the volume 36 toproduce a very rich scanning field having very few gaps. This featurefacilitates the assured scanning of a bar code brought into the patternirrespective of its orientation since the entire bar code will be swept(traversed) by one or more lines. Accordingly, the scanner operator neednot precisely place or orient the bar code within the pattern so long asthe bar code is within the volume and somewhat directed toward thescanner's window.

The means for sweeping the laser beam to create the scan lines 40 makingup the groups may consist of any suitable means, e.g., an oscillatingmirror, an electro-optic scanner, etc. In the preferred embodiment shownherein the beam sweeping means basically comprises a four sided polygon42 arranged for rotation about a rotation axis 44. Each face 46 of thepolygon is reflective, e.g., is a mirror (preferably planar), and tiltedat a different respective angle with respect to the rotation axis. Thus,as the laser beam 48 is swept by the various faces of the polygon (to bedescribed later) it produces the four generally parallel, generallyequidistantly spaced lines 40 of each group. It should be noted that thefaces of the polygon need not be oriented so that the line spacing isequadistant, if a different spacing arrangement is desired.

Referring now to FIGS. 1 and 2-4 details of the construction of thescanner 20 will now be described. Thus, can be seen the housing 28basically comprises a front wall 50, a pair of side walls 52 and 54, atop wall 56, a bottom wall 58 (FIGS. 3 and 4) and a rear wall 60 (FIGS.3 and 4). The housing is preferably formed of two plastic sections 62and 64 which are each integrally molded and which when joined alongtheir respective periphery edges 66 complete the housing. The twosections 62 and 64 of the housing are arranged to be secured togethervia conventional threaded fastening means (not shown) extending throughrespective holes 68 located in the corners of the housing (as shown inFIG. 2).

As can seen in FIGS. 1 and 3 the front wall 50 of the housing 28includes an inclined surface portion 50A at the interface of the frontwall 50 and the top wall 56. It is on the inclined portion that asuitable on/off switch 70 and indicator lights or LED's 72 are located.

The window 30 is located within the front wall 50 and, as can be seen inFIG. 1, is of generally rectangular shape.

The scan pattern 26 is produced by sweeping a sharply defined laser beam48 across various optical components located within the housing. Thesecomponents serve to fold the beam into the desired orientations to formthe lines 40 making up the pattern. The means for producing the beam,focusing it, sweeping it through the housing, folding it and directingit out of the housing window are all mounted on an optical bench 74mounted via fasteners 76, on the inside surface of the rear wall 60 ofhousing section 64 (see FIG. 3). Those components will be described indetail later. Suffice for now to state that those components basicallycomprise a visible laser diode 78 (or any other suitable means forgenerating a laser beam), beam focusing and directing means 80, a beamsweeping mechanism in the form of the four sided rotating reflectivepolygon 4 (described heretofore), plural beam-folding reflecting members82, 84, 86, 88, and 90, and a light collecting system 92.

The light collecting system 92 basically comprises a collecting mirror94, a focusing lens 96, and a transducer 98, e.g., photodiode. The lightcollecting means is arranged to receive the light which is reflected offa bar code held within the scanning pattern to convert the receivedlight into an electrical signal indicative thereof. That signal isprovided to signal processing means and associated decoding means alllocated within the housing 30 on printed circuit boards 100 (to bedescribed later) to effect decoding of the symbol and to provide anelectrical signal indicative of the decoded symbol to the cash register28 or other output device (not shown). The details of the structure andoperation of the light collecting system 92 will be described later.

The optical bench 74, as clearly seen in FIGS. 2-4, is a generallyrectangular, plate-like member which includes a flange 102 extendingalong its two side edges and along its bottom edge. The laser diode 78is fixedly mounted on the optical bench adjacent the bottom edge flangeand is oriented parallel to the bench so that it projects a laser beam48 parallel to the optic bench and in a transverse direction, that isparallel to the transverse axis 34 of the window 30. A beam directingmirror 104 is mounted (e.g., glued) on a bracket 106 disposed oppositethe laser diode. The mirror 104 is angled at approximately 45° to theplane of the optic bench to direct the laser beam 48 upward, that isaway from the optic bench perpendicularly to the window (see FIG. 3).The lower edge flange of the optic bench includes a bracket 108 on whichis mounted another beam directing mirror 110. The mirror 110 is disposedabove the mirror 104 and is oriented at an angle to receive the laserbeam 48 from the mirror 104 and to direct it parallel to thelongitudinal axis 32 toward the rotational axis 44 of the polygon 42.

The polygon is mounted on the rotary output shaft of a motor 112 whichis fixedly mounted on the optical bench so that its rotation axis 44intersects an axis 114. The axis 114 extends parallel to thelongitudinal axis 32 of the window and forms the central longitudinalaxis of the optical components making up the scanner.

As mentioned earlier the polygon 42 basically comprises four reflective,e.g., mirrored, planar surfaces 46. Each of these surfaces extends at arespective acute angle to the axis of rotation 44 of the polygon. Inparticular in the preferred embodiment shown herein one face 46 istilted 2° to the rotation axis, while the other faces are tilted atapproximately 4, 6 and 8 degrees, respectively, to the axis of rotation.The polygon is rotated about the rotation axis, via the motor 112, underpower and control of the electronic circuitry mounted on the printedcircuit boards 100.

The movement of each polygon face about the rotation axis 44 causes thelaser beam 48 reflected off of downwardly extending mirror 110 to sweepthrough an arcuate path in front of and to the sides of the polygonface, to thereby create a scan line which is linear when projected ontoa planar surface. The linear scan line produced by each face is foldedby the beam folding mirrors 82-90 (to be described hereinafter) to forma respective line 40 of each of the respective groups 26A-26E. Inasmuchas the reflective faces 46 of the polygon are each disposed at a slightangle (e.g., 2, 4, 6 and 8 degrees) to the rotational axis 44 eachreflective face of the polygon sweeps the laser beam 48 across adifferent portion of the folding mirrors 82-90, thereby producing theparallel lines 40 (i.e., the "raster") of the various groups.

The details of the reflecting means made up of mirrors 82-90 will now bedescribed. All of the mirrors are of generally planar and are mounted onthe optical bench 74 adjacent the polygon 42 and under the window 30. Inparticular the mirrors 82-90 are mounted via a spider member 116 havingfive angled brackets 118, one for each mirror. The spider 116 secured tothe optical bench 74 via the fasteners 76. Preferably the mirrors 82-90are glued in place on the spider's brackets 118.

As can be seen clearly in FIGS. 2 and 4 the mirror 82 has a transverseaxis defining its width and is mounted so that its transverse axisextends generally perpendicular to the longitudinal central axis 114 ofthe scanner, while being basically centered with respect thereto. Themirror 82 is tilted upward at an angle of approximately 45° to the planeof the window 30. The mirror 82 forms the scan lines 40 making up group26A.

The mirrors 84 and 86 are disposed on opposite sides of the centrallongitudinal axis 114 immediately adjacent the polygon 42. In factportions of the mirrors 84 and 86 extend past the forwardly facing faceof the polygon. Each of the mirrors 84 and 86 extends at a respectivesmall acute angle, e.g. 8°, to the longitudinal axis 114, with each ofthe mirrors being angled upward at approximately 45 degrees to thewindow 30. The mirrors 84 and 86 form the scan lines 40 of groups 26Dand 26E, respectively.

The mirrors 88 and 90 are disposed on either side of the longitudinalcentral axis 114, with mirror 88 being interposed between mirror 82 andmirror 84, and with mirror 90 being interposed between mirror 82 andmirror 86. Each of the intermediate mirrors 88 and 90 has a transverseaxis defining its width. Each transverse axis extends at a substantialacute angle, e.g., 48°, to the central longitudinal axis 114 of the.Moreover, each mirror 88 and 90 is angled upward at approximately 45degrees to the window 30. The mirrors 88 and 90 form the scan lines 40making up the groups 26B and 26C, respectively.

The formation of one line 40 of each group 26A-26E is accomplished asfollows: the rotation of the polygon 42 causes the beam 48 projectedonto one face 46 thereof to be swept across the lateral mirror 86, inthe clockwise direction where viewed in FIG. 2 (to form one line ofgroup 26E) then across mirror 90 (to form one line of group 26C), thenacross mirror 82 (to form one line of group 26A), then across mirror 88(to form one line of group 26B), and finally across mirror 84 (to formone line of group 26D). Inasmuch as each of the mirrors is angled upwardwith respect to the window the sweep of the beam thereacross causes thatmirror to project the laser beam line out of the window, therebyproducing a respective line 40 of each of the groups as described above.Moreover, inasmuch as the next successive face 46 of the polygon 42 isat a slight angle (e.g., 2 degrees) with respect to the proceeding facethe next scan line 40 swept across the mirror 86, 90, 82, 88, and 84,will cross those mirrors at a different location than the beam swept bythe previous polygon face. Accordingly, such action produces a secondrespective scan line 40 of each of the groups 26A-26E.

The foregoing scanning process is carried out by each successive face ofthe polygon a it rotates about the rotation axis to produce the rasteredlines of the groups. The motor is rotated at a very high rate of speed,e.g., in excess of 5,000 rpm so that the scanner produces in excess of400 scans per second.

The details of the light collecting system 92 of the scanner 20 will nowbe described. As mentioned earlier that system is arranged to receivethe light which is reflected off a bar code within the scan patternvolume and which passes back through the window 30 into the interior ofthe housing 28. The light coming back through the window is reflected bythe mirrors 82-90 back to the faces of the rotating polygon, whereuponeach of those faces directs the reflected light to the light collectingsystem, and in particular to heretofore identified collecting mirror 94.

As can be seen clearly in FIG. 2 the collecting mirror 94 basicallycomprises a concave reflecting surface, which in the preferredembodiment is spherical. The mirror is mounted, e.g., glued, onto abracket 120 projecting upward from the optical bench 74 and is spaced infront of the mirror 110. In order to enable the laser beam 48 producedby the laser diode 78 from passing from mirror 110 to the rotatingpolygon 42, the spherical collecting mirror 94 includes a centralopening 122 therein.

The collecting mirror 94 is oriented slightly downward (see FIG. 3) tobe aimed at the polygon. The collecting mirror receives the reflectivelight from each face 46 of the polygon and concentrates or focuses itand directs it to the focusing lens 96. The focusing lens 96, as can beseen in FIGS. 2-4 is mounted opposite the collecting mirror alongcentral longitudinal axis 114 and above the polygon 42. The means formounting the focusing lens at that position comprises a bracket 124fixedly secured to the front portion of the optical bench 74. As can beseen the photodiode 98 is also mounted within the bracket 124, butbehind the lens 96. The lens is arranged to converge or focus the lightreflected by the spherical collecting mirror 94 onto the photodiode 98.

The use of the focusing lens 96 in conjunction with the collectingmirror 94 provides the scanner 20 with a greater depth of field forscanning bar codes then would otherwise be possible with a similarlysmall sized housing. By depth of field it is meant the range ofdistances measured from the window outward that a bar code can beeffectively scanned.

The use of the focusing lens 96 ensures that the light spot which isprojected onto the photodiode is kept sufficiently small for a largerdepth of field than would be possible with the use of the sphericalcollecting mirror alone. Moreover, since the spherical collecting mirrorincludes the central opening 122, absent the lens 96 when scanning barcodes disposed close to the window the image projected from thespherical collecting mirror to the photodetector may include an area ofno light (e.g., the image of the hole 122). Obviously, such action isundesirable. The use of the focussing lens 96 obviates that potentialproblem.

It should be pointed out at this juncture that the light collectingsystem as just described is merely exemplary. Thus, other lightcollecting systems, e.g., a lens, hologram, etc., may be used in lieu ofthe collecting mirror 94 and associated focussing lens 96.

As mentioned earlier, the electronic and various other electricalcomponents for the scanner 20 are mounted on various printed circuit(PC) boards in the housing. Thus, as can be seen one printed circuitboard 100 is mounted, via opposed brackets 126, so that it is disposedimmediately adjacent the bottom wall 58 of the housing 28, while a pairof printed circuit boards 100 are mounted between opposed brackets 128,adjacent one side wall 54 of the housing, and another printed circuitboard 100 is mounted between oppopsed brackets 130 adjacent the otherside wall 52 of the housing. Another small printed circuit board (notshown) is mounted adjacent the front face of a housing near the inclinedportion 50A.

As should be appreciated by those skilled in the art, the patternproduced by the scanner 20 is quite effective for scanning various typesof bar code labels, be they "picket fence" oriented, or "ladder"oriented. However, if a bar code is a truncated and ladder oriented codeand is held a substantial distance from the window, the truncated barcode may be located within a small gap between the lines 40 making upgroups 26D and 26E, i.e., the portion of the pattern designated by thereference numeral 132 in FIG. 5. Merely broadening the raster, that isthe spacing between the various respective lines of the respectivegroups, will not obviate that problem without generating the attendantproblem of creating gaps in the field at other places through whichladder style symbols can slip unread.

Thus, in order to further augment the coverage of ladder orientedsymbols up close to the scanner's window, the side mirrors 84 and 86 maybe modified so that each is split into two parts. This arrangement isshown in the embodiment of the scanner of FIGS. 6 and 7. That scannerproduces a scan pattern like that shown in FIG. 8. In such anarrangement the more vertically oriented scan fields 26D and 26E can bebroadened up close to the window without having an adverse effect at adistance from the window. Thus, one gets the advantage of broadening thefield closely adjacent the window of the scanner, but not generating toobroad a field at the outer distance limit of the depth of field.

The embodiment of the scanner 20 shown in FIGS. 6 and 7 is identical inall respects to that shown in FIGS. 1-4 except that the two sidesmirrors 84 and 86 of the embodiment of FIGS. 1-4 are replaced by twopairs of side mirrors 134 and 136 and 138 and 140, as will be describedhereinafter. In the interest of brevity, all of the identical componentsof the embodiment of FIGS. 1-4 are given the same reference numerals inthe embodiment of FIGS. 6 and 7, and their structure and function willnot be reiterated hereinafter.

As can be seen in FIGS. 6 and 7, a pair of side mirrors 134 and 136 aremounted on one side of the central longitudinal axis 114, (andcorrespond to mirror 84) while a similar and mirror image pair ofmirrors 138 and 140 are mounted on the opposite side of the centrallongitudinal axis (and correspond to mirror 86). The mirrors 134-140 aremounted by respective brackets 118 of the spider and are each orientedso that they extend at the same small acute angle, e.g., 8°, to thelongitudinal axis as the mirrors 84 and 86 described heretofore.Moreover, the mirrors 134 and 136 are parallel to each other, and themirrors 138 and 140 are parallel to each other. The mirrors 134 and 136jointly establish the lines 40 of the group 26D, while the mirrors 138and 140 jointly establish the lines of the group 26E. The spacing, thatis the lateral offset between mirrors 134 and 136, and between mirrors138 and 140 produces two sets of lines in groups 26D and 26E. As can beseen in FIG. 8, the two sets of lines are spaced slightly from eachother so that all of the lines of those groups are not equidistantlyspaced, as is the case in the embodiment of scanner 20 shown in FIGS.1-4. Thus, as shown in FIG. 8, the side groups 26D and 26E of thepattern 26 are closer together, thereby eliminating the gap 132 of thepattern of FIG. 5.

As should be appreciated by those skilled in the art the planes of thepairs of the side mirrors must be parallel. Otherwise, the reflectedportion of the beam coming back off the bar code could not be returnedthrough the return focusing system to the photodetector.

As will be appreciated from the foregoing, the projection scanner 20 asdescribed heretofore, scans omnidirectionally, that is the bar code canbe presented in any orientation within the field. Moreover, the scannerprovides free-hand scanning productivity as heretofore been provided byconventional counter mounted, slot scanners, plus hand-held scanningflexibility as provided heretofore by hand-held scanners. Furtherstill,being of such a small size e.g. 6.5 inches long by 6.5 inches wide by 3inches deep, the scanner is adaptable to fit just about any size, spaceand mounting requirements, and provides a small, unobtrusive foot print.The highly collimated or focused volume of the scan preventsunintentional scanning of nearby projects.

Without further elaboration the foregoing will so fully illustrate ourinvention that others may, by applying current or future knowledge,readily adapt the same for use under various conditions of service.

We claim:
 1. A retroreflective bar code symbol scanning device ofcompact construction, comprising:a compact housing having a planarwindow through which laser light can pass; an optical bench enclosed bysaid housing and having a longitudinal central axis; laser beamproducing means fixedly mounted with respect to said optical bench forproducing, when activated, a laser beam; beam sweeping means fixedlymounted with respect to said optical bench, for receipt of said laserbeam and being arranged for repeatedly sweeping said laser beam about afirst axis in plural paths, said first axis intersecting saidlongitudinal central axis; an array of at least first, second, and thirdstationary reflective surfaces fixedly mounted with respect to saidoptical bench and disposed adjacent said beam sweeping means for receiptof said repeatedly swept laser beam, said first, second, and thirdstationary reflective surfaces being generally disposed under saidwindow, said fist stationary reflective surface having a transverse axisextending substantially perpendicularly to said longitudinal centralaxis, and said second and third stationary reflective surfaces beingdisposed on opposite sides of said longitudinal central axis; lightfocusing means fixedly mounted with respect to said optical bench anddisposed at a height above and immediately adjacent said firststationary reflective surface and having a transverse axis extendingsubstantially perpendicularly to said longitudinal central axis, saidlight focusing means being arranged for the passage of said laser beamthrough said light focusing mean directly to said beam sweeping means;laser light detection means fixedly mounted with respect to said opticalbench, said laser light detection mans being arranged to receive lightfrom said light focusing means and for detecting the intensity of saidreceived light and producing an electrical signal indicative of saiddetected intensity; and control means for activating said laser beamproducing means and said beam sweeping means so as to produce said laserbeam and repeatedly sweep said laser beam about said first axis, andacross said first, second, and third stationary reflective surfaces,thereby producing at least a first, second, and third groups of pluralscan lines, respectively, which are projected out through said windowand intersect about a projection axis which is substantiallyperpendicular to said plane of said window and within a generallyconfined volume extending from immediately adjacent said window toapproximately six inches (62.5 cm) therefrom so as to produce a highlycollimated projected scanning pattern within which a bar code symbol canbe scanned independent of the orientation of said bar code symbol insaid highly collimated scanning pattern, each scan line in said firstgroup of scan lines being substantially parallel to each other scan linein said first group of scan lines, each scan line in said second groupof scan lines being substantially parallel to each other scan line insaid second group of scan lines, and each scan line in said third groupof scan lines being substantially parallel to each other scan line insaid third group of scan lines, whereby when a bar code symbol ispresented to said highly collimated projected scanning pattern withinsaid generally confined volume, said bar code symbol is scanned by saidlaser beam, and at least a portion of the laser light reflected fromsaid scanned bar code symbol is directed through said window, reflectedoff said first, second, and third stationary reflective surfaces towardssaid beam sweeping means and then reflected from said beam sweepingmeans, towards said light focusing means and onto said laser lightdetection means to produce said electrical signal.
 2. Theretroreflective bar code symbol scanning device of claim 1, wherein saidbeam sweeping means comprises an electric motor having a shaft rotatableabout said first axis, and a plurality of rotatable reflective surfacesfixedly mounted with respect to said rotatable shaft, each saidrotatable reflective surface being substantially planar, disposed at adifferent acute angle with respect to said first axis, and rotatingabout said first axis when said electric motor is activated, and whereinsaid device additionally comprises:signal processing means in saidcompact housing, for processing said electrical signal so as to decodesaid scanned bar code symbol and produce data representative of thedecoded bar code symbol, and wherein said control means is disposed insaid compact housing.
 3. The retroreflective bar code symbol scanningdevice of claim 2, wherein said different acute angles are selected sothat the scan lines in each said group of scan lines are substantiallyequidistant from each other at any distance from said window.
 4. Theretroreflective bar code symbol scanning device of claim 1, wherein saidlaser beam producing means comprises a laser diode fixedly mounted withrespect to said optical bench, and wherein said first, second and thirdstationary reflective surfaces comprise first, second and third planarmirrors, respectively, each fixedly mounted with respect to said opticalbench.
 5. The retroreflective bar code symbol scanning device of claim4, wherein said light focusing means comprises a focusing mirror.
 6. Theretroreflective bar code symbol scanning device of claim 1, wherein saidarray of stationary reflective surfaces further comprises:fourth andfifth stationary reflective surfaces, each being adjacent said beamsweeping means and generally disposed under said window, said fourth andfifth stationary reflective surfaces being disposed on opposite sides ofsaid longitudinal central axis between said second and third stationaryreflecting surfaces, respectively, and wherein, as said laser beam isdirected through said light focusing means and reflects from said beamsweeping means, said reflected laser beam is repeatedly swept acrosssaid fourth and fifth stationary reflective surfaces producing fourthand fifth groups of plural scan lines, respectively, which are projectedout through said window, each of the scan lines in said fourth group ofscan lines being substantially parallel to each other scan line in saidfourth group, and each of the scan lines in said fifth group of scanlines being substantially parallel to each other scan line in said fifthgroup of scan lines, said fourth and fifth groups of scan linesintersecting with said first, second, and third groups of plural scanlines within said generally narrow volume.
 7. The retroreflective barcode symbol scanning device of claim 6 wherein each of said scan linesof said second group of scan lines is oriented at a small acute anglemeasured in one direction from said longitudinal axis, and wherein eachof said scan lines of said third group of scan lines is oriented at thesame small acute angle measured in the opposite direction with respectto said longitudinal axis.
 8. The retroreflective bar code symbolscanning device of claim 7 wherein each of said scan lines of saidfourth group of scan lines is oriented at a substantially larger acuteangle measured in one direction with respect to said longitudinal axisthan said small acute angle, and wherein each of said scan lines of saidfifth group of scan lines is oriented at the same substantially largeracute angle measured in the opposite direction with respect to saidlongitudinal axis than said small acute angle.
 9. The retroreflectivebar code symbol scanning device of claim 8 wherein said small acuteangle is approximately eight degrees, and wherein said substantiallylarger acute angle is approximately forty-eight degrees.
 10. Theretroreflective bar code symbol scanning device of claim 7 wherein saidsmall acute angle is approximately eight degrees.
 11. Theretroreflective bar code symbol scanning device of claim 1, wherein saidcompact housing has a height dimension less than about 6.5 inches (16.5cm), a width dimension of less than about 6.5 inches (16.5 cm) and athickness less than about 3 inches (7.6 cm).
 12. The retroreflective barcode symbol scanning device of claim 1, which further comprises;meansfor supporting said compact housing with respect to a counter surface sothat said scanning pattern can be projected at an orientation above saidcounter surface for scanning bar code symbols presented to saidprojected scanning pattern.
 13. The retroreflective bar code symbolscanning device of claim 12, wherein said orientation is laterallyoutward above said counter surface.
 14. The retroreflective bar codesymbol scanning device of claim 1, which further comprises a baseportion comprising means for selectively supporting said compact housingin an orientation above a counter surface so that said scanning patterncan be projected above said counter surface in selected desiredorientations.
 15. The retroreflective bar code symbol scanning device ofclaim 1 wherein each of said scan lines of said second group of scanlines is oriented at a small acute angle measured in one direction fromsaid longitudinal axis, and wherein each of said scan lines of saidthird group of scan lines is oriented at the same small acute anglemeasured in the opposite direction with respect to said longitudinalaxis.
 16. The retroreflective bar code symbol scanning device of claim15 wherein said small acute angle is approximately eight degrees.